Lifetime of molecule

Strickler S J and Berg R A 1962 Relationship between absorption intensity and fluorescence lifetime of molecules J. Chem. Phys. 37 814-22... 

Orientation, Rotation, and Fluorescence Lifetime of Molecules near Surfaces... 

The lifetimes of molecules which undergo allowed transitions in the ultraviolet have radiative lifetimes of the order of 10 8 to 10" 9 sec. If the transition is orbitally forbidden, the radiative lifetime of the excited state is 10"5. 

The first time-resolved investigations on vibrational dephasing and vibrational lifetimes of molecules in the liquid phase were reported in 1971 and 1972 by Kaiser et al. utilizing nonlinear Raman scattering (3,4). A combination of infrared excitation with spontaneous Raman probing... 

Laubereau A, von der Linde D, Kaiser W. Direct measurement of the vibrational lifetimes of molecules in liquids. Phys Rev Lett 1972 28 1162-1165. 

In dilute electrolyte solutions ion-ion interaction as function of electrolyte concentration is fully explained by the Debye-Hiickel-Onsager theory and its further development. The contribution of ion solvation is noticed, if, for instance, the mobilities at infinite dilution of an ion in different solvent media or as function of ionic radii as considered. Up till now the calculation of that dependence has been only rather approximateAn improvement is quite probable, though, theoretically very involved if the solvent is not regarded as a continuum, but the number and arrangement of solvent molecules in the primary solvation shell of an ion is taken into consideration. Also the lifetime of molecules in the solvation shell must be known. Beyond this region a continuum model of ion-solvent interaction may be sufficient to account for the contributions of solvent molecules in the second or third sphere. 

Another matter concerns the time of reaction between a set of water molecules after an ion has just pushed its way into the middle of them. Thus, if the lifetime of molecules in the primary solvation shell is sufficiently short, there must be somejumps in which the ion is bare or at least only minimally clothed. How is the hydration number affected by the time needed for the solvent molecules buried in the solvent layer to break out of that attachment and rotate so that their dipoles are oriented toward the ion to maximize the energy of interaction (cos 0 = 1) ... 

There exists some circumstantial evidence linking interstellar molecules to protostars. The more complex interstellar molecules tend to occur only in regions of very high density ( 10 H /cm ), e.g. the infrared nebula in Orion. Star formation proceeds at a rapid rate in such clouds, and thus solar nebulae may have formed and dissipated. The lifetime of our solar nebula seems to have been rather short 10 to 10 yr, or 1-2 orders of magnitude less than the age of a typical cloud, e.g. the Orion Nebula, or lifetimes of molecules against UV photolysis (Gammon, 1978). 

The lifetimes of molecules in the lowest excited singlet state are typically of the order of 10 -10 s. Typical... 

In this approach, the excited-state lifetime of molecules is measured by following the decay of their fluorescence. The electron injection rate ( j) is calculated from the measured fluorescence decay rate (kobs) and the intrinsic radiative (kf) and non-radiative (A nr) excited decay rates through the relationship... 

Strickler, S. J., Berg, R. A., Relationship between Absorption Intensity and Fluorescence Lifetime of Molecules, J. Chem. Phys. 1962, 37, 814 822. 

The lifetimes of molecules in the lowest excited singlet state are typically of the order of 10 "-10 7 s. Typical rates of proton transfer reactions are 10" s 1 or less. Consequently, excited-state proton transfer may be much slower, much faster, or competitive with radiative deactivation of the excited molecules. 

As shown above, the electronic relaxation in small molecules may be more efficient than the vibrational relaxation within the same electronic state. If, moreover, one of interacting electronic states is nonradiative, that is, if the lifetime of molecules transferred to the /> state is much longer than that of the 5> state, new specific deactivation chaimels may play an important role. The usual path of vibrational relaxation within the j manifold collision-induced transitions from initially excited nth to (o— l)th vibronic level may be less efficient than a many-step process involving... 

Although C2H4 ligands do have characteristic IR bands, the relevant regions of the spectrum were always obscured by the absorptions of the SCC2H4 solvent used for the synthesis of the ethene complexes listed in the table. These were, therefore, identified by comparison with literature data and by NMR, either before [18,19] or after isolation of the conipound [6,30]. There is a lower limit on the lifetime of molecules that can be observed in SCF, by use of photochemistry and conventional FTIR. The precise limit depends on the optical arrangement but is usually a few seconds. Nevertheless, much shorter-lived complexes, such as CpRe(CO)2Xe, can be detected in SCF by use of time-resolved IR spectroscopy [31] (see chapter 3.1). 

In section 9.3.2, we have seen that spectral shifts of incarcerated guests can provide insight into the electronic and spatial characteristics of the inner phase. Of special interest to the photophysical community are also excited state lifetimes of molecules enclosed in constrained media. Investigation of these systems may lead to the development of novel photophysical probes for immunoassays and devices for information storage or solar-energy conversion. Parola et al. investigated the photophysical properties of 9-cyanoanthracene (CA) inside hemicarcerand 26 (Figures 9.3 and 9.34). ... 

An understanding of atomic and molecular interactions and collisions is essential to the study of cold and ultracold molecules. Collisions govern the lifetime of molecules in traps and determine whether proposed cooling schemes will work. Once atoms and molecules are in the ultracold regime, the extent to which their interactions can be controlled depends on a detailed understanding of their collisional properties. The purpose of this chapter is to outline atomic and molecular collision theory and describe the special features that are important to the study of cold molecules. 

Weitz DA, Garoff S, Hanson CD et al (1982) Fluorescent lifetimes of molecules on silver-island films. Opt Lett 7 89-91... 

Introduction of a physically significant function k(r) can explain an increase of the artificial reaction distance a. Determination of a and D is easy from the experimental point of view and allows us to compute k(r) with adequate set of values (k, b), in particular if lifetime of molecule is short and viscosity of solvent is large. 

The lifetimes of molecules in the lowest excited singlet state are typically 10 1 -10 s. Typical rates of proton transfer reactions are <10i°s i. Consequently, excited state proton transfer may be much slower, much faster, or competitive with radiative deactivation of the excited molecules. If excited state proton transfer is much slower than fluorescence, the relative fluorescence intensity will vary with pH exactly the same way as does the absorbance, reflecting only the ground-state acid-base equilibrium. If excited state proton transfer is much faster than fluorescence, the fluorescence intensity will vary with pH in a way that reflects the acid-base equilibrium in the lowest excited singlet state. Equilibrium in the excited state is a rare phenomenon and will not be dealt with further here. 

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